我有这个数据结构声明:
zero
我通过以下代码手动将字段注册到[ProtoContract]
public class NotACollectionHolder
{
public NotACollection some_objects;
}
[ProtoContract(IgnoreListHandling = true, ImplicitFields = ImplicitFields.AllPublic)]
public class NotACollection : IEnumerable<int>
{
public int some_data;
// something looks like a collection API
public void Add(int a) { }
public IEnumerator<int> GetEnumerator() { throw new NotImplementedException(); }
IEnumerator IEnumerable.GetEnumerator() { throw new NotImplementedException(); }
}
:
MetaType
我用MetaType meta = RuntimeTypeModel.Default.Add(typeof(NotACollectionHolder), false);
ValueMember member = meta.AddField(1, "some_objects", itemType: null, defaultType: null);
string proto = Serializer.GetProto<NotACollectionHolder>();
标记NotACollection
。我试图通过提供IgnoreListHandling
来强制AddField
忽略NotACollection
看起来像集合的事实。
尽管如此,我itemType: null, defaultType: null
不为空,member.ItemType
也不为空。 member.DefaultType
已成为生成的some_objects
中的repeated
字段:
proto
我希望message NotACollectionHolder {
repeated int32 some_objects = 1;
}
看起来像这样:
proto
我怎样才能实现这一目标?我究竟做错了什么?我如何强制protobuf-net像非收集字段一样处理这个字段?
提前致谢。
答案 0 :(得分:0)
我认为这可能是RuntimeTypeModel
API的错误或限制。
确定ValueMember
是否为集合的方法是RuntimeTypeModel.ResolveListTypes()
。当传入的itemType
为空时,它会尝试推断集合项类型。仅使用静态属性为NotACollectionHolder
构建合同时,例如:
var model = TypeModel.Create();
var schema = model.GetSchema(typeof(NotACollectionHolder));
然后调用ProtoBuf.Meta.MetaType.ApplyDefaultBehaviour(bool isEnum, ProtoMemberAttribute normalizedAttribute)
来创建初始化ValueMember
。它有以下逻辑:
// check for list types
ResolveListTypes(model, effectiveType, ref itemType, ref defaultType);
// but take it back if it is explicitly excluded
if(itemType != null)
{ // looks like a list, but double check for IgnoreListHandling
int idx = model.FindOrAddAuto(effectiveType, false, true, false);
if(idx >= 0 && model[effectiveType].IgnoreListHandling)
{
itemType = null;
defaultType = null;
}
}
请注意IgnoreListHandling
的明确检查?这可以正确地阻止some_objects
被序列化为集合。
相反,如果以编程方式添加ValueMember
,如下所示:
var model = TypeModel.Create();
var meta = model.Add(typeof(NotACollectionHolder), false);
var member = meta.AddField(1, "some_objects", null, null);
var schema = model.GetSchema(typeof(NotACollectionHolder));
ResolveListTypes(model, miType, ref itemType, ref defaultType);
请注意,IgnoreListHandling
没有检查?这是导致问题的原因。
不幸的是,ValueType.itemType
是只读的,而MetaType[int fieldNumber]
只是get-only,所以似乎没有一个简单的API可以调用来解决这个问题。您可以考虑reporting an issue。
我能找到的唯一解决方法是引入NotACollectionHolder
类型的代理:
[ProtoContract]
internal class NotACollectionHolderSurrogate
{
[ProtoMember(1)]
internal NotACollectionSurrogate some_objects;
public static implicit operator NotACollectionHolder(NotACollectionHolderSurrogate input)
{
if (input == null)
return null;
return new NotACollectionHolder { some_objects = input.some_objects };
}
public static implicit operator NotACollectionHolderSurrogate(NotACollectionHolder input)
{
if (input == null)
return null;
return new NotACollectionHolderSurrogate { some_objects = input.some_objects };
}
}
[ProtoContract]
internal class NotACollectionSurrogate
{
[ProtoMember(1)]
public int some_data;
public static implicit operator NotACollection(NotACollectionSurrogate input)
{
if (input == null)
return null;
return new NotACollection { some_data = input.some_data };
}
public static implicit operator NotACollectionSurrogate(NotACollection input)
{
if (input == null)
return null;
return new NotACollectionSurrogate { some_data = input.some_data };
}
}
然后做:
var model = TypeModel.Create();
model.Add(typeof(NotACollectionHolder), false).SetSurrogate(typeof(NotACollectionHolderSurrogate));
var schema = model.GetSchema(typeof(NotACollectionHolder));
生成的合同是必需的:
message NotACollectionHolderSurrogate {
optional NotACollectionSurrogate some_objects = 1;
}
message NotACollectionSurrogate {
optional int32 some_data = 1 [default = 0];
}
答案 1 :(得分:0)
我发现这确实是protobuf-net中的一个错误。修复它的第一种方法是更改protobuf-net的源代码:在函数文件MetaType.cs中
if (model.FindWithoutAdd(miType)?.IgnoreListHandling == true)
{
itemType = null;
defaultType = null;
}
else
ResolveListTypes(model, miType, ref itemType, ref defaultType);
替换行
itemType
与
defaultType
另一种方法是在添加字段后使用反射将对象ValueMember
的私有字段null
和ValueMember m = meta.AddField(++last_field_number, f.Name, f.ItemType, f.DefaultType);
m.GetType().GetField("itemType", BindingFlags.NonPublic | BindingFlags.Instance).SetValue(m, null);
m.GetType().GetField("defaultType", BindingFlags.NonPublic | BindingFlags.Instance).SetValue(m, null);
设置为sqoop import --connect jdbc:mysql://localhost:3306/hadoopguide --table widgets --username <username> --password <password> --split-by id -m 1 --hive-import;
:
sqoop create-hive-table --connect jdbc:mysql://localhost:3306/hadoopguide --table widgets --username <username> --password <password> --fields-terminated-by ',';
希望这会对某人有所帮助。